Fuel Testers & Gauges

Fuel Testers

Aircraft fuel testers are handheld devices used during pre-flight inspections to check the quality of fuel directly from the aircraft's fuel sumps (drain points). The primary purpose is to detect:

  • Contaminants: The most common contaminants are water (which is heavier than fuel and settles at the bottom of the tank) and sediment/debris. Water can freeze at altitude, blocking fuel lines, or cause engine failure.

  • Correct Fuel Type: Testers help visually confirm the fuel's color (e.g., 100LL avgas is blue) and consistency, ensuring the correct type of fuel has been loaded into the aircraft. Misfueling (e.g., putting jet fuel in a piston engine) can have catastrophic consequences.

Pilots typically drain a small sample of fuel into a clear plastic cup (the fuel tester) and visually inspect it for clarity, color, and the presence of any water beads or particles. Some testers also have features like a screwdriver tip for opening cowlings or a larger reservoir for multiple sump drains.